Marine propeller with removable blades

ABSTRACT

A fluid motor is provided in association with each blade of a marine propeller of the type having removable blades to assist in removing the associated blade.

Umted States Patent 1191 [111 3,71 1,220

Ramback et al. 1 1 Jan. 16, 1973 [541 MARINE PROPELLER WITH [56] References Cited REMOV BLE BLADES A UNITED STATES PATENTS [75] lnventors: Carl-Gustaf Ramback; Nils Olol Er- 2 415 42 M De Filip 6/89 p1 bmh Krstmehamn' 2,981,338 4/l96l Hindmarchm. ..416/207 x we 3,358,772 12/1967 Bunyan ..416/244 x [73] Assignee: Aktiebolaget Karlstads Mekanlska g; 1" ct i as ey Karlstad Swede 3,557,744 1 1971 Herbert ..114 57 x [22] Filed: Feb. 19, 1971 Primary ExaminerEverette A. Powell, Jr. [21] APP! 116337 Attorney-Brumbaugh, Graves, Donohue & Raymond [30] Foreign Application Priority Data [57] ABSTRACT April 10, 1970 Sweden ..4912 70 A fluid is Pwvided assmiatim, with each blade of a marlne propeller 0f the type havmg remova- 52 us. c1. ..416/146, 416/158, 416 204, ble blades remwmg blade- 416/207 5 Claims, 1 Drawing Figure [51] Int. Cl. ..B63h l/20 [58] Field of Search ..416/244, 146, 207, 158, 204,

MARINE PROPELLER WITH REMOVABLE BLADES BACKGROUND OF THE INVENTION This invention relates to marine propellers of the type having removable blades and, in particular, to a system for assisting in removing the blades.

Some marine propellers have blades that are individually mounted on a propeller hub and may be removed from the hub for repair or replacement. Variable pitch marine propellers, for example, have removable blades. With propellers having removable blades it is advantageous that the propeller assembly, as installed on a ship, be constructed such that the individual blades can be removed and replaced without removing the entire propeller assembly from the propeller shaft.

Usually, each blade of a propeller having removable blades has a flange at the root end that is received within a recess on the propeller hub. The blade flange and the recess are provided with matching guide edges and one or more locating pins that assist in guiding the blade into the recess and retaining it in proper position. The hub of most variable pitch propellers is filled with oil, and sealing rings are generally used between the blade flanges and the blade recesses on the hub to isolate the oil chamber. Removable propeller blades are normally secured to the hub by bolts that extend through holes in the blade flanges and are received in threaded holes in the hub.

In some cases the holes in the blade flanges are elongated slots and allow each blade to be rotated about an axis generally radially of the axis of rotation of the propeller to enable the blade pitch to be altered to suit the requirements of the particular propeller installation by merely loosening the bolts, rotating the blade in its recess mounting to the desired pitch and retightening the bolts. With this type of propeller there is frequently considerable difficulty in changing the pitch of the blades without damaging the seals and the guide edges between the blade flange and the recess at the propeller position on the hub. Such damage can occur, particularly with relatively large and heavy blades, because of the frictional forces developed between contacting surfaces of the blade flanges and the recesses on the hub.

It has been proposed heretofore that hydraulic fluid be injected under pressure into the space between a propeller blade flange and the receiving recess on the hub to generate a force tending to lift the blade from the hub and make it easier to turn and to overcome the frictional force. However, this arrangement requires seals between the blade flange and the hub, and it has been found that the seals are easily damaged and rendered ineffective to hold the required pressure and to overcome the basic difficulty involved in rotating the blade.

With variable pitch propellers difficulty is also encountered when removing the blade, particularly if it is of large size and weight. Frequently the blade must be rotated on its mounting before it can be removed. Basically the operation of removing a blade from a variable pitch propeller is not very much different from that involved in removing a fixed but adjustable pitch blade.

SUMMARY or THE INVENTION There is provided, in accordance with the present invention, an improvement in propeller assemblies of the type having removable blades that facilitates the removal of the blades and overcomes the problems referred to above. In particular, the invention provides for, first, substantially eliminating the frictional forces that impede rotation of a blade on its mounting so that it may be relatively easily rotated and, second, for lifting the blade a relatively substantial distance from its mounting into a position that will facilitate its ultimate removal.

More particularly, a fluid motor is provided in association with each blade for displacing the associated blade generally radially outward, relative to the axis of rotation of the propeller, upon communication of a fluid pressure to the motor. The fluid motor may be a hydraulic piston that is received in a cylinder formed in each blade flange or in the hub at each blade site. In the first case, the piston of each blade is urged inwardly toward the hub by hydraulic fluid pressure developed in the head of the cylinder, and an extension portion on the piston engages the hub and generates forces in the cylinder reacting inwardly against the piston and outwardly against the blade thereby to urge the blade away from the propeller hub. In the second case, fluid pressure acts outwardly against a piston having an extension portion that is engagable with the associated propeller blade flange and acts inwardly against the hub. In either instance, the piston extension portion serves as a force transmitting element to physically, through engagement of the extension portion with either the hub or the blade, provide a reaction force operating in association with an expandable fluid chamber that also applies a force in a direction opposite to that applied through the piston extension against the head end of the cylinder.

The arrangement, according to the invention, considerably facilitates removing the blade, insofar as Accordingly, provides for eliminating a substantial part of the the frictional forces developed between the blade and its mounting site on the hub. Accordingly the propeller blade can be rotated with almost no risk of damage to he blade mounting site or to the blade flange. The arrangement does not require any seals in the flange and the hub mounting, and, of course, the possibility of damage to such seals is therefore nonexistent. It is particularly advantageous to provide a fluid motor that has a stroke sufficient to lift the blade away from the hub a distance such that the blade flange completely clears the extremities of the hub. Once the blade is lifted away from the hub by the fluid system, according to the invention, it need only be moved longitudinally by appropriate lifting equipment to enable its complete removal from the propeller assembly.

The fluid motor system can also be used to facilitate remounting of a blade. When the blade is moved into position for remounting, the motor is operated to transfer the weight of the blade from the ancillary lifting equipment to the fluid system, and the system is then controlled to lower the blade back into position and to facilitate rotating the blade to proper orientation for final attachment. With propeller assemblies of the type having fixed, but adjustable pitches, the system of course provides considerable advantages in making it easy to adjust and set the pitches of the blades.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As just mentioned, the drawing illustrates the root and flange portions only of one blade I, and those skilled in the art will certainly understand that the propeller assembly includes three, four or perhaps more blades spaced about the circumference of a propeller hub. The fluid motor arrangement and the mounting arrangement of the blade illustrated in the drawing are representative of the arrangement employed for all blades of the propeller assembly.

Each blade I of the propeller has a flange 3 attached to or formed integrally with the root portion of the blade. Ordinarily, the flange 3 will be circular in plan, that is; in a plane perpendicular to the plane of the drawing sheet. The flange 3 of each blade is received in a matching recess 7 formed in the propeller hub 9, the recess and flange being provided with companion guide edges 11 that interfit, and with one or more locating pins 13, which are preferably arranged to be removed from outside of the flange 3. The guide edges 11 and pins 13 assist in locating and retaining the blade in position on the hub.

In the embodiment, the fluid motor system includes a cylinder 15 formed in the blade flange and having a head end at the top that is communicated by a passage 17 with a fitting 19 through which fluid under pressure may be introduced into the head end of the cylinder. The cylinder receives a piston 21 having an appropriate seal 23 and provided with an extension portion formed with or secured to the base of the piston and extending toward the propeller hub 9. The end of the extension portion of the piston 21 is engageable with a seat 25 formed on the propeller hub, the end of the extension portion and the seat being of matching shape to maintain the axis of the piston in alignment with the cylinder upon engagement between the extension portion and the hub seat. In addition, a guide bushing 27 is installed in the base of the cylinder 15 to assist in guiding the piston axially of the cylinder. A spring 29 is located in the annular space between the piston extension portion and the wall of the cylinder and is compressed between the base of the piston 21 and the bushing 27 so that it urges the piston 21 in an upward direction toward the head of the cylinder, thus, normally retaining the piston retracted upwardly into the cylinder and retaining the extension portion out of engagement with the propeller hub 9. A stop ring 31 received in a groove in the extension portion of the piston near the bottom end of the extension engages the bushing 27 to limit the extent of the retraction of the piston into the cylinder.

In operation, each blade of the propeller assembly may be relocated in its hub recess, such as may be desired in a fixed, but adjustable, pitch propeller, or for removal by first rotating the propeller to position the blade that is to be adjusted or removed at the top or 12 oclock position. The bolts and locating pin 13 are loosened, or removed, and a source of hydraulic fluid under pressure is connected to the fitting l9. Fluid under pressure is then introduced into the head portion of the cylinder through the passage 17, thereby generating a force on the piston 21 against the return spring 29 downwardly so that the extension portion is engaged against the seat 25 on the hub 9. The application of pressure in the head of the cylinder also generates a force in the head portion of the cylinder that acts against the head in an upward direction tending to offset the weight of the propeller and ultimately to exceed the weight of the propeller and lift the propeller off the hub. The force generated may, of course, be only sufficient to remove part of the weight of the blade from the hub, thereby to reduce the frictional engagement between the blade flange and the hub and enable the blade to be rotated. The application of greater pressure can, of course, actually take up the entire weight of the blade and ultimately lift it out of position in the recess 7 If the fluid motor has a sufficient stroke, the delivery of additional fluid under pressure into the head of the cylinder 15 will lift the blade a substantial distance up from the hub so that the lower extremities of the blade clear the upper extremities of the hub, thereby allowing the blade to be removed by moving it parallel to the axis of rotation of the propeller.

It will be readily apparent to those skilled in the art that a cylinder and piston can be installed in the hub of the propeller assembly at each blade position, each piston being movable toward the corresponding blade to shift the blade away from the hub. Such arrangement is, in essence, simply a relocation of the fluid motor and does not involve any departure in principle or result from the embodiment illustrated in the drawing. Thus, the embodiment is intended to be merely exemplary, and those skilled in the art will be able to make numerous variations and modifications of it without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention, as defined in the appended claims.

We claim:

1. In a marine propeller assembly having a plurality of blades, each of which is removably mounted on a hub at a blade position, the hub and blades having complementary engaging portions, the engaging portion of each blade being a flange part at its root and the hub having a blade-engaging portion at each blade position, the improvement of a device for urging each blade away from the hub for removal therefrom comprising fluid-actuated piston means associated with each blade and within the propeller assembly for displacing the associated blade generally radially outward relative to the axis of rotation of the propeller, and means for communicating actuating fluid to the piston means from a location externally of the assembly, the piston means including a cylinder in one of said complementary engaging portions at each blade position, a piston in the cylinder, and a piston extension part on the piston and movable upon fluid actuation into engagement with the other of said complementary engaging portions at each blade position.

2. An improvement according to claim I wherein the cylinder of the piston means for each blade is located in the blade, and the piston extension part on the piston is movable upon fluid actuation into engagement with the hub at the corresponding blade position.

3. An improvement according to claim 1 further comprising resilient return means for restraining each piston against the movement thereof tending to displace the corresponding blade outwardly.

4. An improvement according to claim 1 wherein the blade is located on the hub for pivoting relative to the hub about an axis lying substantially in a radial-axial plane of the propeller, and wherein each piston means is positioned to act at and along the pivot axis of the associated blades.

5. In a marine propeller assembly having a plurality of blades, each of which is removably mounted on a hub and has a flange portion at its root for engagement at a blade position with the hub, the improvement of a device for urging each blade away from the hub for removal therefrom comprising in association with each blade an inwardly open cylinder formed in the blade flange, a piston received in the cylinder in sealing and sliding engagement with the cylinder walls and having an extension portion associated with it and located to engage a portion of the propeller hub at the corresponding blade position, resilient means for urging the piston away from the hub, and a passage through the blade flange communicating with a head part of the cylinder that is on the opposite side of the piston from the hub and leading to the exterior of the blade flange thereby to enable a fluid under pressure to be introduced into said head part of the cylinder and generate a force on the piston effective to urge it toward the hub and to engage the piston extension portion with the hub and to generate a force acting at the head of the cylinder and effective to remove the blade away from the hub. 

1. In a marine propeller assembly having a plurality of blades, each of which is removably mounted on a hub at a blade position, the hub and blades having complementary engaging portions, the engaging portion of each blade being a flange part at its root and the hub having a blade-engaging portion at each blade position, the improvement of a device for urging each blade away from the hub for removal therefrom comprising fluid-actuated piston means associated with each blade and within the propeller assembly for displacing the associated blade generally radially outward relative to the axis of rotation of the propeller, and means for communicating actuating fluid to the piston means from a location externally of the assembly, the piston means including a cylinder in one of said complementary engaging portions at each blade position, a piston in the cylinder, and a piston extension part on the piston and movable upon fluid actuation into engagement with the other of said complementary engaging portions at each blade position.
 2. An improvement according to claim 1 wherein the cylinder of the piston means for each blade is located in the blade, and the piston extension part on the piston is movable upon fluid actuation into engagement with the hub at the corresponding blade position.
 3. An improvement according to claim 1 further comprising resilient return means for restraining each piston against the movement thereof tending to displace the corresponding blade outwardly.
 4. An improvement according to claim 1 wherein the blade is located on the hub for pivoting relative to the hub about an axis lying substantially in a radial-axial plane of the propeller, and wherein each piston means is positioned to act at and along the pivot axis of the associated blades.
 5. In a marine propeller assembly having a plurality of blades, each of which is removably mounted on a hub and has a flange portion at its root for engagement at a blade position with the hub, the improvement of a device for urging each blade away from the hub for removal therefrom comprising in association with each blade an inwardly open cylinder formed in the blade flange, a piston received in the cylinder in sealing and sliding engagement with the cylinder walls and having an extension portion associated with it and located to engage a portion of the propeller hub at the corresponding blade position, resilient means for urging the piston away from the hub, and a passage through the blade flange communicating with a head part of the cylinder that is on the opposite side of the piston from the hub and leading to the exterior of the blade flange thereby to enable a fluid under pressure to be introduced into said head part of the cylinder and generate a force on the piston effective to urge it toward the hub and to engage the piston extension portion with the hub and to generate a force acting at the head of the cylinder and effective to remove the blade away from the hub. 